Fume hoods are commonly used when personnel are handling potentially harmful materials, particularly substances that give off noxious fumes. Fume hoods can often be found in educational, industrial, medical and government laboratories and production facilities. A typical fume hood may include a housing within which the harmful materials may be stored and used. Users typically access the interior of the fume hood housing through an opening, which in some cases, may be selectively opened and closed via one or more movable sashes or the like. The fume hood housing is typically vented by a ventilation device so that air and potentially harmful gases or other materials within the housing are positively exhausted out of the building through ductwork. Such venting typically draws fresh air in through the fume hood opening, which helps keep any potentially harmful materials within the fume hood and out of the space where personnel may be located.
Proper control of the airflow through a fume hood may be important for safety, cost, comfort and/or other reasons. For example, if airflow through the fume hood opening is too low (e.g., the velocity of air flowing through the opening or face velocity is too low), contaminants inside the fume hood may have an opportunity to exit the fume hood. This may present a safety issue. However, maintaining a high volume airflow through the fume hood at all times may be wasteful because unnecessarily large volumes of conditioned air (e.g., cooled or heated air) within the building may be drawn into the fume hood and exhausted. As a result, additional air must be conditioned and supplied to the building to replace the exhausted air.